I watch enough low quality exploitation B movies and big budget sci fi blockbusters
to have developed a very forgiving attitude towards 'suspension of disbelief'...

So I just give a generous dose of benefit of the doubt to any post apocalyptic action genre films and TV shows...

For instance, that never ending supply of bullets ?

I'll just presume a return to pre-industrial-revolution manufacturing methods.

i.e blokes out in their sheds making their own black powder and lead moulded projectiles,
then haphazardly refilling spent bullent casings.

Of which there would be a plentiful supply, at least in post civilisation collapse USA....

Btw I finally got round to wathing "Open Range" last night.
A truly excellent 'naturalistic' cowboy film..
Except for one jarring instant when Kevin Costner manages to get something like 17 continuous shots
without reloading his 1870s pistol....???